Question

Trying to determine the concentration of a DCPIP solution, you were able to find out that it took 15mL of 0.001M ascorbic acid solution to turn 4 mL of the DCPIP solution clear. What is the concentration of the DCPIP solution?

Answer 1

DICHLOROPHENOLINDOPHENOL IS A PINK COLOUR DYE SOLUTION WHICH IS USED AS OXIDANT , OXIDISING ASCORBIC ACID TO DEHYDROASCORBIC ACID BY DCPIP.

[Two of the four hydroxy groups in the ascorbic acid are oxydised to keto groups by DCPIP during titration]

1 EQUIVALENT OF DCPIP = 1 EQUIVALENT OF ASCORBIC ACID.

SO BY RULE OF TITRATION -------------------

Molarity of ascorbic acid x volume of ascorbic acid = Molarity of DCPIP x volume of DCPIP

15 ml x 0.001M = 4 ml x M_dcpip

concentration of DCPIP , M_dcpip =  15 ml x 0.001M/4 ml

= 0.00375M

concentration of DCPIP = 0.00375 moles /litre